Increasing occupational and environmental exposure to metals and metal-based compounds, which are inherently toxic to biological systems, raises concerns about their potential effects on the health and well being of living organisms. Exposure to such metals is a significant problem that affects a large and diverse segment of the population. Five of the top 20 hazardous substances (including the top three hazardous substances) on the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) Priority List of Hazardous Substances for 2003 are metals, including arsenic, lead, mercury, cadmium, and chromium (hexavalent). In 2003, exposures to lead were the number 1 environmental health hazard for children.
Exposure to metals may occur in a wide variety of locations, including in the workplace, in homes or schools, or in the outdoor environment. Skin contact is one significant route of exposure to metals or metal compounds, at least, because (i) metals may be absorbed through the skin; (ii) skin can act as a reservoir for metals; (iii) skin surface deposition can be an important source of secondary contamination; and (iv) impairment or loss of skin barrier function can occur. Unfortunately, many metals typically are not simply washed off of the skin. Surveys of industrial wash rooms show most potentially contaminated workers invest less than 60 seconds cleaning up before breaks. However, most conventional industrial soaps require 5 to 10 minutes of continuous washing to reduce surface concentrations of powdered metals (such as, lead) to levels that are not likely to present potential health hazards. Thus, significant metal contamination may remain after washing (Esswein and Tepper, NIOSH Health Hazard Evaluation Report No. 91-0366-2453, Delaware County Resource Recovery Facility, Chester, Pa., CDC/NIOSH:Cincinnati, Ohio, 1991; Esswein et al., NIOSH Health Hazard Evaluation Report No. 94-0268-2618, Standard Industries, San Antonio, Tex., CDC/NIOSH:Cincinnati, Ohio, 1996, Mattorano, NIOSH Health Hazard Evaluation Report No. 94-0273-2556, Bruce Mansfield Power Station, Shipping port, PA, CDC/NIOSH:Cincinnati, Ohio, 1996).
Lead provides a particularly useful example of the challenges posed by metal exposure. Lead exposure can occur, for example, to workers involved (and others in the area) in removal of lead-based paints and/or the renovation of structures containing lead-based paints, workers in metal working and other metal related industries, workers in other industrial facilities, as well as adults or children living within or visiting homes or schools containing lead-based paints. Prolonged and repeated exposure to workers involved in removal or abatement of lead-based paints and exposure of children in homes and schools is especially damaging. Lead residues on human skin, especially on the hands, of industrial workers (as well as others) can be a significant health risk since such residues may be ingested during normal activities (e.g., eating, drinking, and smoking).
Methods for detecting the presence of lead are available. While such detection methods may be useful to disclose the presence or absence of lead, detection methods are not designed to remove lead from the surface tested. Compositions and methods are needed to remove metals, such as lead.
To that end, efforts have been directed to removing lead from liquids, including drinking water (see, e.g., U.S. Pat. Nos. 5,665,240; and 6,106,725), liquid hydrocarbons (see, for example, U.S. Pat. Nos. 4,424,120; 4,424,119; and 5,952,541), machining coolant solutions (see, e.g., U.S. Pat. No. 5,520,815), phosphoric acid (see, e.g., U.S. Pat. No. 5,431,895), and other aqueous solutions (see, e.g., U.S. Pat. Nos. 4,010,186; 4,956,154; 4,994,191; 5,053,139; and 5,286,464). Lead desorption from contaminated soil has also been described (see, e.g., Komecki et al., Environ. Geosci., 6(1):42-52, 1999). The physical properties of liquids and soil permit physical mixing of contaminated liquids or soils with decontaminating agents on a microscopic level that cannot be achieved with non-dispersible (such as, solid) matter. As a result, it may be more difficult to contact and remove metal contamination from a solid surface, especially where the surface has interstices where contaminants can lodge (such as, skin). Moreover, agents suitable for lead decontamination of liquid or soil may cause damage to solid surfaces and, in particular, may irritate or harm sensitive surfaces such as human skin.
Comparatively few methods of removing lead or other potentially harmful metals from a solid surface are described. Lead-containing paint provides one application; however, the described methods involve harsh physical methods (e.g., hot air blowers combined with scraping) and/or caustic chemicals (such as, methylene chloride, toluene, acetone, calcium hydroxide, magnesium hydroxide, and sodium hydroxide; see, e.g., U.S. Pat. No. 5,964,961). These methods are unsuitable for applications where no substantial modification or damage to the surface is desired; such as, for example, removal of lead (or other metals) from human skin.
Products that claim to remove lead from human skin contain active ingredients such as EDTA (see, Askin and Volkmann, Am. Ind. Hyg. Assoc. J., 58:752-753, 1997) or anionic surfactants (see, D-Wipe®; Esca Tech, Inc.; Milwaukee, Wis.). EDTA is a suspected persistent environmental pollutant and a skin irritant, which may cause reddening or inflammation on prolonged skin contact. Anionic surfactants may also cause skin irritation, such as dryness and scaling, and may further lead to high levels of foaming. Moreover, anionic surfactants may not be fully effective in removing lead contamination.
It is desirable, therefore, to provide safe, reliable and effective compositions and methods for removing metals, such as lead, from surfaces, including human skin. Of particular need are compositions and methods that do not substantially damage the treated surface, or unduly irritate biological surfaces, such as skin.